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Luke, Pics of the clutch disks would be helpful.

I am new to the Transaxle world, but I spent 19 years developing and testing Automatic transmissions for the OEM world. In my opinion, I would plan on replacing the clutches. They have to be damaged from heat if they have been slipping. Whether they are the cause or a casualty, is the question.

You said you checked the clutch engagement pressure. Did you read it at Pressure Test Port #2 with a warmed up Hydrostat? If so, then that strongly points to a failed clutch as the root cause, maybe due to some abuse. Replacing the clutch might be all you need to do.

If measured elsewhere, then there could be other causes such as a torn or cut piston seal, sticking regulator valve, or a bad solenoid.

Again, I am new to JD transaxles, but it fits fairly well into my professional experience.

Luis
 

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Discussion Starter #43
Hey Luis

Test was done on the upper right hand side port as shown in attached picture from manual. I'm pretty sure that is test port #2. Pressure was 220psi.

I will take apart the clutch pack now to inspect the plates.

Luke.
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Looks right to me when comparing to Tuff Torque manual.

I think the answer will be obvious when you pull them apart. In automatics, if the fluid smelled like burned coffee, you knew the clutches were failed. But, if the fluid was changed before you got it, the smell may not be there.

Regardless, I am expecting to see failed clutches at this point. It is finding the root cause of the failure that I am focused on. With good pressure, I would say it was simply abused at some point, replace the clutches, and hope for the best.

Luis
 

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Yes, plates have a lot of discoloration. Does this indicate excessive heat from slipping/excessive wear?
Yes the discoloration is from the heat. It probably has more damage dome to the steel plates then the friction plates. The steel plates are more then likely wrapped from the heat.
 

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Discussion Starter #46
Here are the clutch plates. They look pretty bad to me..

The oil was quite dark when I drained it.
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Luke is the brake shoe worn alot also? The manual says (Replace brake shoe if grooves in shoe contact surface are not visible.)is the contact surface the part that looks polished in pic of your clutch pack? In manual it looks like grooves are suppose to be there.
Wonder if the previous owner never used the rio bypass when he backed up? Alot of starts and stops on a big 60"7iron deck.
 

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Discussion Starter #48
No the shoe isn't in my pictures. But you are right. The manual does say that there should be grooves in the contact surface of the shoe. I will check in the morning, but I don't think the shoe that I removed had any grooves. Will probably have to order a new brake shoe also.

It does look like the clutch pack surface had grooves in it in the manual also. But it specifically says that only the brake shoe should have grooves. So confusing..
 

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Yea it is i had to read it a few times too.
 

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Those clutch disks are cooked. As expected or worse.

My concern now is that all that clutch debris could interfere with hydraulic valve operation. Ideally, I would want to clean out the transaxle completely including the valvebody, depending on how well the filter has trapped the debris. I would want to inspect the screens on the solenoids and clean or replace as appropriate.

Again, I am speaking from my expereince with automotive transmissions. Somebody else with actual K90 rebuild experience should weigh in here.

I would be interested in seeing the old filter cut open and element inspected. Not that it matters that much. But, it might give an indication if the bypass opened. (Well, maybe. maybe not.)

Luis
 

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Discussion Starter #51
All of the pressures from the test ports checked out fine, so perhaps I dodged a bullet in regards to clutch debris. I will try to clean as much as possible though without dismantling the whole transaxle.

I'm yet to pull the solenoid, so I will definitely do that and make sure that it is nice and clean.

Might be interesting to see inside the filter.. I don't think I've thrown it out yet. Will check.
 

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Luke have you started pricing parts yet? I use www.greenfarmparts.com or www.greenpartstore.com for the 2nd if you use it you can get free shipping with ttwt code. For first one use code gtt code for i thing 3or 4% off.first one has free shipping if the total is high enough.
Hope they sell just parts and not one complete unit but the manual does talk about replacing alot of other items if you do this or that. Then again i just had a thought, it might a item only deere or tt sells. Might look some when im back home tonite.
 

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Luke just got home and did some parts searching. Ok greenfarmparts has part for what they call plate kit (clutch)$211.40 pn am878397. for the (complete) gear and clutch kit $734.67 pn mia 881599. Now springs orings ect ect thats not included with just clutch plates. WoW
 

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Nice research Summers5.

Luke, assuming there were no extraneous noises and no other obvious damage to the hard parts. I would just get the Plate Kit am878397 that Summers5 found. (The more expensive kit is not something you are likely to need, in my opinion)

In addition, I would get the piston o-ring or "packing" CH11572. It is only $2.60. My thought is that the clutch debris might have caused it to wear. It should be relatively easy to replace. (Might need to use compressed air on the fill port to pop it out. Then be very careful putting the new one on and reassembling so as not to cut it. Use fluid to lube it when reinstalling)

I think you are going to be quite happy with the results when this is done.

Good luck,
Luis
 

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Discussion Starter #55
Thanks Summers5. I'm in Australia, so my only option really is buying from John Deere Australia. I've ordered the clutch pack, which here comes to a staggering $450. I really do appreciate you looking up suppliers and prices though! Very kind of you.

Luis - The John Deere parts guy I ordered the clutch pack through suggested I also order the relevant o-rings, which I assume are the ones you referred to. There were no other noises with the tractor - I was actually quite impressed with how quiet the PTO system was when engaged. So I am looking forward to installing the new clutch and seeing what this beast of a tractor is capable of.
 

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Luke, wait. Is your x748 right hand drive?

:p
 

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Right hand driver seat now thats something to see must discharge on the left side also.lol Didnt evan cross my mind where you were must make anything John Deere really rare over there. One more reason to keep her running good;-).
 

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My wife is a genius. I was telling her about your clutch failure and she asked if it could be low on fluid. Of course! It has a leak!

The previous owner let it run low until the pump could not pick up enough fluid. If it can't suck in the fluid, it will not make enough pressure to keep the clutch from slipping. So, the clutch slipped while they were running the lawn mower; it overheated and failed. End of story.

So, if you know where the fluid was leaking, I would definitely try to fix it.

Luis (<---currently worshiping his wife.)
 

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Seen that video - very informative. Do you have a video showing the removal of the clutch? Was it fairly straight forward to inspect the clutch plate wear?

I checked the pressures out of the output pump and clutch engagement pressure. All were within spec. This tells me surely I have a clutch plate wear problem?
Got a little behind in my replies. I can’t remember which part of the 8 that has the clutch removal in it.

Based on the measurements of your clutch you need a replacement or at minimum plates. I’d pull it apart and see what it looks like.... and go from there.
 
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